With the explosive growth in the biotechnology and medical technology fields and the ever increasing emphasis on accuracy and efficiency within these burgeoning technologies, a need was created for a device that could transfer precisely measured amounts of fluid. Thus, the peristaltic pump, a mechanism for moving fluids through a flexible tube was developed and has become well known in the art, particularly in the bio-technical and medical fields and in connection with analytical instruments and detectors, as well as in other fields.
Peristaltic pumps typically include engagement mechanisms rotatably mounted on a shaft so that rotation of the shaft causes the engagement mechanisms to move in a defined circular path where the engagement mechanism is intermittently brought into pressure contact with a flexible length of tubing to compress and re-compress the tubing and thereby force liquid through the tubing. Typical peristaltic pump arrangements handle a single tube at a time.
Attempts have been made to use peristaltic pumps to effect the blending or dispensing of different solutions. These attempts have brought to the surface problems with prior art peristaltic pumps, particularly when two or more different fluids are desired to be mixed in predetermined measured amounts. At times it is desired to provide precisely the same flow through two or more peristaltically pumped tubes. Calibration of a series of independently operated peristaltic pumps, particularly when the same flow rates are desired, is extremely difficult and time consuming.
Another problem associated with prior art peristaltic pumps has been the undesirable pulsation of the fluid as it is moved through the pump to its desired location. This is extremely undesirable where a steady flow rate of the desired fluids is required, such as in proportional dispensing or blending of nutrient solutions. Undesirable pulsation can lead to accuracy reduction.
A drawback of some prior art peristaltic pumps occurs with pumps which require feeding of a free end of the tube in and through an opening in the pump. This is not possible when the tube is connected at its ends, such as to a source of fluid and to the receiver to which the fluid is to be pumped. Peristaltic pumps of this type require the operator to plan ahead so the tube is fed through the pump before connections are completed or to disconnect the tube from the source or the receiver, which is time consuming and leads to possible contamination of the pumping system.
Still another drawback of prior art peristaltic pumps is the need for individual drive means or motors for each peristaltic pump when more than one peristaltic pump is employed in a given operation. Adding pumps increases the cost of equipment, torque and power and increases the space required. For example, it has now been appreciated that having a dual dispensing channel device will require less torque than that needed for two single channel pumps run by the same motor.
Finally, there has been a tendency in prior art peristaltic pumps for the flexible tubing to "walk" or move longitudinally through the pump while the pump is being driven by the external motor or other driving device. Spring loaded locks and similarly operating devices have been employed in the past in an effort to prevent such walking; however, such devices are relatively complex and require manual adjustment each time a tube of a different diameter is placed into the peristaltic pump.
It is therefore a general object of the present invention to provide an improved peristaltic pump for moving fluids through flexible tubing.
It is a further object of the present invention to provide an improved peristaltic pump for moving fluid through a flexible tube that has increased accuracy when compared with pumps having fewer engagement mechanisms rotated within the pump.
Still another object of the present invention is to provide a single peristaltic pump that will dispense fluid through two flexible tubes disposed in two independent pathways where the fluid moving through each flexible tube has precisely the same flow rate for identical tubes, or if tubes are used which have different internal diameters, the resulting flow rates are proportional to the cross-sections of the respective tubes used.
Another object of this invention is to provide a dual pumping device which requires less torque than that needed for two separate pumps run by a single motor and handling the same tubes and fluids as can be handled by the dual channel device of this invention, thereby allowing a less powerful motor to drive the dual channel device than is required to drive two single-channel peristaltic heads run from a single motor.
It is yet a further object of the present invention to provide a peristaltic pump that allows a series of pumps to be mounted piggyback on a single motor drive unit.
Yet another object of the present invention is to provide an improved peristaltic pump having a holding means that prevents the flexible tube from walking while the pump is activated and that automatically and passively accommodates tubing of differing diameters.
Another object of this invention is to provide a dual channel peristaltic pump which is suitable for biotech applications, such as "bleeding/feeding" bioreactors or fermentors, wherein an equal amount of nutrient solution needs to replace what is removed during harvesting or sampling.
Another object of the present invention is to provide a peristaltic pump suitable for one or more uses such as sample introduction into analytical instruments and detectors, proportional dispensing or blending of nutrient solutions, multiple dosing, liquid extraction or sample enrichment procedures, color blending of paints and inks, proportional pumping of plating bath additives, plating bath replenishment, water purification, for example where dispensing of chlorine or of purifiers is necessary, effluent sampling in waste water or sewage treatment, maintaining proper pH or other ion values, preparative liquid chromatography applications, such as producing step gradients having differing ratios of different buffers, high precision, high accuracy liquid metering, pharmaceutical production or dispensing, computer disk manufacturing for example dispensing slurries in the final production step of hard disk drives, enrichment of milk and other beverages, dispensing fuel oil additives, fluid sampling, fluid control, brewery addition and blending, supplementing livestock feed, medical diagnostic production, medical research metering, production line dispensing, reagent control, metering or dispensing for plastics production, and recirculation pumping.
These and other objects, advantages and features of the present invention will become apparent from the following description of the preferred embodiments of the present invention considered in conjunction with the accompanying drawings.